title: Entomological investigation and control of a chikungunya cluster in Singapore.
abstract: In August 2008, a team from the National Environmental Agency conducted an entomological investigation of a chikungunya cluster in Singapore, with the primary aim of identifying the vector responsible for the outbreak and to assess the vector control operation. A total of 173 adult mosquitoes were caught using both the sweep-net method and the BG Sentinel Traps in and around the affected workers' quarters. Of these, 120 (69.4%) were Aedes albopictus and the rest were Culex quinquefasciatus. More than 2700 Ae. albopictus larvae were also collected from 33 breeding habitats detected. No Aedes aegypti was found. During the preintervention period, 6 (8.4%) out of 71 adult female Ae. albopictus were found positive for the chikungunya virus (CHIKV). Vector control measures resulted in a 90% reduction of adult Ae. albopictus caught by BG Sentinel Traps. Postintervention surveillance revealed the presence of CHIKV-positive mosquitoes. These findings led to continued intensive vector control operation in the affected area that further reduced vector population and interrupted the transmission of the disease. The E1 gene sequence of the CHIKV was identical to those of CHIKV isolated from human chikungunya cases working in the affected area, and contained the A226V mutation. The incrimination of Ae. albopictus as a major vector involved in the transmission of A226V CHIKV had led to the revision of chikungunya control strategy in Singapore. This study suggests the benefit of a vector control program that includes the evaluation of control measures in conjunction to virological surveillance in vector population.
authors.affiliation: Environmental Health Institute, National Environmental Agency, Singapore, Singapore.
authors.forename: Cheong Huat
authors.initials: CH
authors.lastname: Tan
authors.forename: Pei Sze Jeslyn
authors.initials: PS
authors.lastname: Wong
authors.forename: Mei Zhi Irene
authors.initials: MZ
authors.lastname: Li
authors.forename: Siok Yin Sharon
authors.initials: SY
authors.lastname: Tan
authors.forename: Tze Kwang Caleb
authors.initials: TK
authors.lastname: Lee
authors.forename: Sook Cheng
authors.initials: SC
authors.lastname: Pang
authors.forename: Sai Gek
authors.initials: SG
authors.lastname: Lam-Phua
authors.forename: Nasir
authors.initials: N
authors.lastname: Maideen
authors.forename: Ah Bah
authors.initials: AB
authors.lastname: Png
authors.forename: Sin Ying
authors.initials: SY
authors.lastname: Koou
authors.forename: Deng
authors.initials: D
authors.lastname: Lu
authors.forename: Lee-Ching
authors.initials: LC
authors.lastname: Ng
mesh_terms: D000330:Aedes / Q000821:virology*; D018354:Alphavirus Infections / Q000453:epidemiology / Q000517:prevention & control* / Q000635:transmission; D000818:Animals; D065632:Chikungunya Fever; D002646:Chikungunya virus / Q000235:genetics / Q000302:isolation & purification*; D016000:Cluster Analysis; D003465:Culex / Q000821:virology*; D004196:Disease Outbreaks / Q000517:prevention & control; D004772:Entomology; D005260:Female; D006801:Humans; D007303:Insect Vectors / Q000821:virology*; D008297:Male; D009032:Mosquito Control / Q000379:methods*; D057147:Mosquito Nets; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017421:Sequence Analysis; D012846:Singapore / Q000453:epidemiology